Rapid growth of network traffic promotes constant growth of line card capacities of routers and transport equipment. With the development of the optical communications industry, technologies related to optical transceiver components are also evolving. High-rate, low-cost, low-power consumption, and miniaturized optical components gradually become a hotspot to which the industry pays attention.
Currently, in most client-side optical modules, a directly modulated laser (DML) or an electro-absorption modulated laser (EML) is used as a transmit-side device. The directly modulated laser has advantages of low costs, miniaturization, and the like, and is widely used in the field of short-distance interconnections.
Optical modulation is superimposing a signal that carries information on a carrier lightwave. Modulation enables a parameter of a carrier lightwave to change with a change of a signal superimposed on the carrier lightwave. These parameters include an amplitude, a phase, a frequency, polarization, a wavelength, and the like of the lightwave. A modulated lightwave that carries information is transmitted in a fiber, and demodulated by an optical receiving system to detect required information. Optical output of an existing directly modulated laser (mainly a lightwave amplitude is modulated) may change with a parameter of the laser. The most commonly used modulation of laser output is performing amplitude modulation by controlling a current that flows through a device, or obtaining an amplitude modulation output by changing a parameter of a resonant cavity.
However, an optical eye diagram output by an existing directly modulated laser during high-speed modulation is nearly closed. After fiber transmission, it is difficult to perform decision and recovery at a receiving part. If an external filter is used, a size of the device is relatively large and integration is difficult to perform.